Study Explores BHA Damage Caused by Trapped Torque During Drillpipe Connection

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 223695, “Case Study of BHA Damages Caused by Sudden Release of Trapped Torque During Drillpipe-Connection Process” by Aaron Simon, SPE, and Denis Li, SPE, SLB. The paper has not been peer reviewed. _ This paper presents a study of three cases in which release of trapped torque occurs during drillpipe connection, leading to bottomhole-assembly (BHA) damage. It highlights the contributing factors and root causes of the trapped-torque-release events and proposes prevention and mitigation measures for these transient events. Analysis suggests that no single universal connection procedure works perfectly for all applications. Ultimately, the risk of the overspeed event vs. the time and steps required to prevent or minimize the consequences must be considered to optimize the procedure. Introduction Release of trapped torque is a dysfunction present during the slip phase of stick/slip. It also occurs when a mud motor stall releases, and it is worsened if established motor-stall-mitigation procedures are not executed properly. What is new about the phenomenon is the evolution in and expanded usage of high-performance polycrystalline diamond compact drill bits and upgraded downhole mud-motor power sections. The industry also has transitioned more wells toward a slimhole well design (4¾-in. nominal BHA outer diameter used to drill smaller production section hole sizes). Improvements to motor technology enable the motor to output more torque, and upgrades to bit designs have made bits more capable of harnessing that torque and delivering improved rates of penetration (ROP). The slimhole BHA design is more pliable because of smaller outer diameters and thinner wall thicknesses of the BHA components, which allow for torque to be trapped within the BHA. The connection practices that present the most significant risk of a sudden release of trapped torque include leaving the bit on bottom during the connection and not drilling off enough at the end of the stand before picking up off bottom. Other practices, such as initiation of rotation at surface without mud circulation, also can be damaging, but those practices are more universally understood to be potentially damaging activities. Trapped-Torque-Release Cases Leading to Damages The following cases are representative of the types of damage that can occur as a result of trapped-torque release during connections. Three cases are presented in the complete paper; two are included in this synopsis. The case involving a motor-connection back-off incident can be found in the complete paper. All cases are from Permian Basin slimhole production section rotary-steerable-system (RSS) BHAs where the measurement-while-drilling (MWD) tool is positioned between the mud motor and the RSS in the BHA design to facilitate transmission of real-time RSS data to surface. Permian Basin cases were simplest to research because of the large quantity of slimhole runs and the propensity of operators in the basin to place emphasis on fast connection times. Cases in other basins do exist; however, those cases are less frequent and evidence is not as compelling as it is in the cases analyzed in this study.